Snap Debs - I've just come into my 27th week and agree with you that it's just starting to get a bit uncomfortable! My local pool has lanes set aside in the deep diving pool for aqua jogging, and provides these big foam waistband things that people strap on - I guess they keep you floating and upright. There are some fairly large people doing that, and I would imagine it's a good workout. I've put on only a very small amount of weight since the initial few months TBH. I have been sticking to a very regular daily eating pattern since the MS ended - porridge and prunes for breakfast (thus combating one of the other less than glamorous effects of pregnancy!) and some wholegrain toast with marmalade, salmon / cheese / egg sandwiches and an apple for lunch, dinner is usually protein and veg / salad (the OH is a low GI / Atkins - style eater, I usually just add a handful of pasta / rice / potatoes to whatever he has). My biggest downfall is probably morning tea at work - scone and jam at 10am!
Have fun and good luck. I think late pregnancy isn't really the time to worry overly about putting on more weight. Eat sensibily, keep on the move when you can and leave the weight loss until afterwards. I'm more into damage limitation that trying to be overly controlled at this stage!